// Copyright 2011 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/deoptimizer.h"
#include "src/macro-assembler.h"
#include "src/register-configuration.h"
#include "src/safepoint-table.h"

namespace v8 {
namespace internal {

#define __ masm->

    // This code tries to be close to ia32 code so that any changes can be
    // easily ported.
    void Deoptimizer::GenerateDeoptimizationEntries(MacroAssembler* masm,
        Isolate* isolate,
        DeoptimizeKind deopt_kind)
    {
        NoRootArrayScope no_root_array(masm);

        // Unlike on ARM we don't save all the registers, just the useful ones.
        // For the rest, there are gaps on the stack, so the offsets remain the same.
        const int kNumberOfRegisters = Register::kNumRegisters;

        RegList restored_regs = kJSCallerSaved | kCalleeSaved;
        RegList saved_regs = restored_regs | sp.bit() | ra.bit();

        const int kDoubleRegsSize = kDoubleSize * DoubleRegister::kNumRegisters;
        const int kFloatRegsSize = kFloatSize * FloatRegister::kNumRegisters;

        // Save all double FPU registers before messing with them.
        __ Dsubu(sp, sp, Operand(kDoubleRegsSize));
        const RegisterConfiguration* config = RegisterConfiguration::Default();
        for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
            int code = config->GetAllocatableDoubleCode(i);
            const DoubleRegister fpu_reg = DoubleRegister::from_code(code);
            int offset = code * kDoubleSize;
            __ Sdc1(fpu_reg, MemOperand(sp, offset));
        }

        // Save all float FPU registers before messing with them.
        __ Dsubu(sp, sp, Operand(kFloatRegsSize));
        for (int i = 0; i < config->num_allocatable_float_registers(); ++i) {
            int code = config->GetAllocatableFloatCode(i);
            const FloatRegister fpu_reg = FloatRegister::from_code(code);
            int offset = code * kFloatSize;
            __ Swc1(fpu_reg, MemOperand(sp, offset));
        }

        // Push saved_regs (needed to populate FrameDescription::registers_).
        // Leave gaps for other registers.
        __ Dsubu(sp, sp, kNumberOfRegisters * kPointerSize);
        for (int16_t i = kNumberOfRegisters - 1; i >= 0; i--) {
            if ((saved_regs & (1 << i)) != 0) {
                __ Sd(ToRegister(i), MemOperand(sp, kPointerSize * i));
            }
        }

        __ li(a2, Operand(ExternalReference::Create(IsolateAddressId::kCEntryFPAddress, isolate)));
        __ Sd(fp, MemOperand(a2));

        const int kSavedRegistersAreaSize = (kNumberOfRegisters * kPointerSize) + kDoubleRegsSize + kFloatRegsSize;

        // Get the bailout is passed as kRootRegister by the caller.
        __ mov(a2, kRootRegister);

        // Get the address of the location in the code object (a3) (return
        // address for lazy deoptimization) and compute the fp-to-sp delta in
        // register a4.
        __ mov(a3, ra);
        __ Daddu(a4, sp, Operand(kSavedRegistersAreaSize));

        __ Dsubu(a4, fp, a4);

        // Allocate a new deoptimizer object.
        __ PrepareCallCFunction(6, a5);
        // Pass six arguments, according to n64 ABI.
        __ mov(a0, zero_reg);
        Label context_check;
        __ Ld(a1, MemOperand(fp, CommonFrameConstants::kContextOrFrameTypeOffset));
        __ JumpIfSmi(a1, &context_check);
        __ Ld(a0, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
        __ bind(&context_check);
        __ li(a1, Operand(static_cast<int>(deopt_kind)));
        // a2: bailout id already loaded.
        // a3: code address or 0 already loaded.
        // a4: already has fp-to-sp delta.
        __ li(a5, Operand(ExternalReference::isolate_address(isolate)));

        // Call Deoptimizer::New().
        {
            AllowExternalCallThatCantCauseGC scope(masm);
            __ CallCFunction(ExternalReference::new_deoptimizer_function(), 6);
        }

        // Preserve "deoptimizer" object in register v0 and get the input
        // frame descriptor pointer to a1 (deoptimizer->input_);
        // Move deopt-obj to a0 for call to Deoptimizer::ComputeOutputFrames() below.
        __ mov(a0, v0);
        __ Ld(a1, MemOperand(v0, Deoptimizer::input_offset()));

        // Copy core registers into FrameDescription::registers_[kNumRegisters].
        DCHECK_EQ(Register::kNumRegisters, kNumberOfRegisters);
        for (int i = 0; i < kNumberOfRegisters; i++) {
            int offset = (i * kPointerSize) + FrameDescription::registers_offset();
            if ((saved_regs & (1 << i)) != 0) {
                __ Ld(a2, MemOperand(sp, i * kPointerSize));
                __ Sd(a2, MemOperand(a1, offset));
            } else if (FLAG_debug_code) {
                __ li(a2, kDebugZapValue);
                __ Sd(a2, MemOperand(a1, offset));
            }
        }

        int double_regs_offset = FrameDescription::double_registers_offset();
        // Copy FPU registers to
        // double_registers_[DoubleRegister::kNumAllocatableRegisters]
        for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
            int code = config->GetAllocatableDoubleCode(i);
            int dst_offset = code * kDoubleSize + double_regs_offset;
            int src_offset = code * kDoubleSize + kNumberOfRegisters * kPointerSize + kFloatRegsSize;
            __ Ldc1(f0, MemOperand(sp, src_offset));
            __ Sdc1(f0, MemOperand(a1, dst_offset));
        }

        int float_regs_offset = FrameDescription::float_registers_offset();
        // Copy FPU registers to
        // float_registers_[FloatRegister::kNumAllocatableRegisters]
        for (int i = 0; i < config->num_allocatable_float_registers(); ++i) {
            int code = config->GetAllocatableFloatCode(i);
            int dst_offset = code * kFloatSize + float_regs_offset;
            int src_offset = code * kFloatSize + kNumberOfRegisters * kPointerSize;
            __ Lwc1(f0, MemOperand(sp, src_offset));
            __ Swc1(f0, MemOperand(a1, dst_offset));
        }

        // Remove the saved registers from the stack.
        __ Daddu(sp, sp, Operand(kSavedRegistersAreaSize));

        // Compute a pointer to the unwinding limit in register a2; that is
        // the first stack slot not part of the input frame.
        __ Ld(a2, MemOperand(a1, FrameDescription::frame_size_offset()));
        __ Daddu(a2, a2, sp);

        // Unwind the stack down to - but not including - the unwinding
        // limit and copy the contents of the activation frame to the input
        // frame description.
        __ Daddu(a3, a1, Operand(FrameDescription::frame_content_offset()));
        Label pop_loop;
        Label pop_loop_header;
        __ BranchShort(&pop_loop_header);
        __ bind(&pop_loop);
        __ pop(a4);
        __ Sd(a4, MemOperand(a3, 0));
        __ daddiu(a3, a3, sizeof(uint64_t));
        __ bind(&pop_loop_header);
        __ BranchShort(&pop_loop, ne, a2, Operand(sp));
        // Compute the output frame in the deoptimizer.
        __ push(a0); // Preserve deoptimizer object across call.
        // a0: deoptimizer object; a1: scratch.
        __ PrepareCallCFunction(1, a1);
        // Call Deoptimizer::ComputeOutputFrames().
        {
            AllowExternalCallThatCantCauseGC scope(masm);
            __ CallCFunction(ExternalReference::compute_output_frames_function(), 1);
        }
        __ pop(a0); // Restore deoptimizer object (class Deoptimizer).

        __ Ld(sp, MemOperand(a0, Deoptimizer::caller_frame_top_offset()));

        // Replace the current (input) frame with the output frames.
        Label outer_push_loop, inner_push_loop,
            outer_loop_header, inner_loop_header;
        // Outer loop state: a4 = current "FrameDescription** output_",
        // a1 = one past the last FrameDescription**.
        __ Lw(a1, MemOperand(a0, Deoptimizer::output_count_offset()));
        __ Ld(a4, MemOperand(a0, Deoptimizer::output_offset())); // a4 is output_.
        __ Dlsa(a1, a4, a1, kPointerSizeLog2);
        __ BranchShort(&outer_loop_header);
        __ bind(&outer_push_loop);
        // Inner loop state: a2 = current FrameDescription*, a3 = loop index.
        __ Ld(a2, MemOperand(a4, 0)); // output_[ix]
        __ Ld(a3, MemOperand(a2, FrameDescription::frame_size_offset()));
        __ BranchShort(&inner_loop_header);
        __ bind(&inner_push_loop);
        __ Dsubu(a3, a3, Operand(sizeof(uint64_t)));
        __ Daddu(a6, a2, Operand(a3));
        __ Ld(a7, MemOperand(a6, FrameDescription::frame_content_offset()));
        __ push(a7);
        __ bind(&inner_loop_header);
        __ BranchShort(&inner_push_loop, ne, a3, Operand(zero_reg));

        __ Daddu(a4, a4, Operand(kPointerSize));
        __ bind(&outer_loop_header);
        __ BranchShort(&outer_push_loop, lt, a4, Operand(a1));

        __ Ld(a1, MemOperand(a0, Deoptimizer::input_offset()));
        for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
            int code = config->GetAllocatableDoubleCode(i);
            const DoubleRegister fpu_reg = DoubleRegister::from_code(code);
            int src_offset = code * kDoubleSize + double_regs_offset;
            __ Ldc1(fpu_reg, MemOperand(a1, src_offset));
        }

        // Push pc and continuation from the last output frame.
        __ Ld(a6, MemOperand(a2, FrameDescription::pc_offset()));
        __ push(a6);
        __ Ld(a6, MemOperand(a2, FrameDescription::continuation_offset()));
        __ push(a6);

        // Technically restoring 'at' should work unless zero_reg is also restored
        // but it's safer to check for this.
        DCHECK(!(at.bit() & restored_regs));
        // Restore the registers from the last output frame.
        __ mov(at, a2);
        for (int i = kNumberOfRegisters - 1; i >= 0; i--) {
            int offset = (i * kPointerSize) + FrameDescription::registers_offset();
            if ((restored_regs & (1 << i)) != 0) {
                __ Ld(ToRegister(i), MemOperand(at, offset));
            }
        }

        __ pop(at); // Get continuation, leave pc on stack.
        __ pop(ra);
        __ Jump(at);
        __ stop("Unreachable.");
    }

// Maximum size of a table entry generated below.
#ifdef _MIPS_ARCH_MIPS64R6
    const int Deoptimizer::table_entry_size_ = 2 * kInstrSize;
#else
    const int Deoptimizer::table_entry_size_ = 3 * kInstrSize;
#endif

    bool Deoptimizer::PadTopOfStackRegister()
    {
        return false;
    }

    void FrameDescription::SetCallerPc(unsigned offset, intptr_t value)
    {
        SetFrameSlot(offset, value);
    }

    void FrameDescription::SetCallerFp(unsigned offset, intptr_t value)
    {
        SetFrameSlot(offset, value);
    }

    void FrameDescription::SetCallerConstantPool(unsigned offset, intptr_t value)
    {
        // No embedded constant pool support.
        UNREACHABLE();
    }

#undef __

} // namespace internal
} // namespace v8
